The potential environmental and health problems of the explosives 2,4,6-trinitrotoluene (TNT) and cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) has increased the progress of technologies that remediate contaminated groundwater, soil, and structures. Areas contaminated from nitro explosives, such as TNT and RDX, are caused by the incomplete detonation of nitro explosives in munitions areas as well waste streams from industrial production areas. These sources of contamination have brought about the dispersal of TNT and RDX in soil and groundwater as well as the remains of explosive residue on structures according to J. C. Pennington, et al in Thermochimica Acta 384, 163-172, and reported by Pennington et al. in U.S. Army Corps of Engineers, Engineer Research and Development Center Report # ERDC TR-05-2, Distribution and Fate of Energetics on DoD Test and Training Ranges: Interim Report 5, April 2005.
The toxicity and mutagenicity of RDX and TNT according to G. T. Peters et al in Environ. Toxicol. Chem. 10, 1073-1081 (1991) and B. Lachance et al in Mutation Research 444, 25-39, (1999) have led to regulation and legislation by the EPA to advance remediation technologies and maintain and protect the environment from present and future contamination of TNT and RDX in the environment as discussed in U.S. Environmental Protection Agency, Office of Drinking Water, Washington, D.C. (1988) and U.S. Environmental Protection Agency, Solid Waste and Emergency Response (5306W) EPA530-F-97-045 (1997).
Remediation research includes the remediation of nitro explosive contamination on scrap metal and ordnance according to C. M. Jung et al. in Biodegradation 15, 41-8 (2004), while the majority of the work centers on removal of explosives from contaminated soil as discussed by F. Ahmad et al. in J. of Contaminant Hydrology 90, 1-20 (2007) and groundwater contamination as discussed by E. P. H. Best et al. in Chemosphere 38, 3383-96 (1999) and S. Y. Oh et al. in Water Sci. & Technol. 54, 47-53 (2006).
Current research has employed phytoremediation as discussed by N. K. Hannink et al., in Critical Reviews in Plant Sciences 21, 511-538 (2002) and microbial techniques disclosed by M. Kulkarni et al in J. of Environ. Management 85, 492-512 (2007) and B. Clark et al in J. of Haz. Mat. 143, 643-648 (2007). These biological remediation technologies are inexpensive and require low energy use in comparison to other remediation methods, however, these techniques have limitations which include slower kinetic rates as confirmed by Kulkami et al in J. of Environ. Management 83, (2007) supra and the suitability for degrading lower level nitro explosive contamination as discussed by Z. Snellinx, et al in Environ. Set. Polka. Res. 9, 48-61 (2002).
Other research has focused on the use of metals to degrade nitro explosives. Some of the metals previously investigated include the use of complexed iron according to D. Kim et al in Environ. Sci. Technol. 41, 1257-1264 (2007) and zero-valent iron (ZVI) discussed by J. Z. Bandstra et al in Environ. Sci. Technol. 39, 230-238 (2005) and S. Y. Oh et al. Water Sci. & Technol. 54, (2006) supra, TiO2 palladium photocatalysis are disclosed by H.-S. Son et al. in Chemosphere 57, 309-317 (2004) and R. Dillert et al. in Chemosphere 30, 2333-2341 (1995), and nickel discussed by M. E. Fuller et al in Chemosphere 67, 419-427 (2007). The use of ZVI is typically restricted to anaerobic conditions, limited pH ranges as reported by Y. Mu et al. in Chemosphere 54, 789-794 (2004), and degradation rates can be constrained by surface corrosion. The use of ZVI in anaerobic conditions results in the production of 2,4,6-triaminotoluene (TAT), which is considered more hazardous than the parent TNT contamination according to Bandstra et al. in Environ. Sci. Technol. 39 (2005) supra.
Commonly known hydrogenation and reduction catalysts include palladium (Pd) and nickel (Ni), and these catalysts have been investigated for the successful remediation of these nitro explosives under ambient temperatures, pressures, and pH conditions. These remediation techniques, however, may require hydrogen sources and reaction vessels purged with hydrogen gas according to Fuller et al. in Chemosphere 67, (2007) supra and C. J. McHugh et al. in Chem. Commun. 2514-2515 (2002). The reaction conditions for these remediation techniques would make them less appropriate for in situ treatment of nitro explosive contamination.
The transition metals, Pd and Ni, are overall less susceptible to surface corrosion, which is advantageous over the use of only ZVI. Combining transition metal catalysts with ZVI has been successfully reported to reduce chlorinated compounds according to D. M. Cwiertny et al. in Environ. Sci. Technol. 40, 6837-6843 (2006). The degradation mechanics of TNT and RDX by mechanically alloying Fe with Pd and Ni is explored in the present invention.
Magnesium was chosen as a potential substrate in addition to ZVI. Magnesium is thermodynamically favored over the extensively used ZVI as a reductive metal because Mg has a greater reduction potential as that compared to ZVI:
                              Mg                      2            +                          +                  2          ⁢                      e            -                              →                        Mg          0                ⁢                                  ⁢                  E          0                      =                  -        2.37            ⁢      V                                    Fe                      2            +                          +                  2          ⁢                      e            -                              →                        Fe          0                ⁢                                  ⁢                  E          0                      =                  -        0.44            ⁢      V      Magnesium also has a self-limiting oxide layer unlike the easily corroded ZVI. Magnesium combined with the hydrogenation catalyst palladium has been explored as a reductive catalytic system and has been shown to reduce chlorinated aromatics as disclosed by E. Hadnagy et al. in J. of Environ. Sci. and Health Part A 42, 685-695 (2007) and U. D. Patel et al in J. of Hazardous Mat. 147, 431-438 (2007) thus the use of magnesium-palladium alloy (MgPd) as a reductive catalytic system for nitroaromatics and other nitro explosives shows potential.
Triacetone triperoxide (TATP) is a cyclic peroxide explosive that is easily prepared using commonly found materials: hydrogen peroxide, acetone, and an acid catalyst as discussed by N. A. Milas et al in J. Am. Chem. Soc. 82, 3361-3364 (1959). TATP has become more frequently used by terrorists according to L. Block in Terrorism Monitor 4, 1-2 (2006), as well as used by clandestine chemists according to J. G. Cannon in The Oklahoman (Mar. 1, 2006) due to its ease in synthesis.
TATP has higher vapor pressure than many explosives and is especially sensitive to heat or friction, making it inappropriate for industrial production, therefore, TATP is not regarded as an environmental contaminant. However, TATP contamination can be found in underground production labs as well as targets of terrorist attacks. These contaminated areas pose a threat to both the public as well as the law enforcement personnel. The sensitivity of TATP makes the safe clean up of TATP a challenging problem resulting in the need for a secure and quick in situ destruction and clean-up method.
Currently, TATP destruction is restricted to reacting TATP with copper at a low pH as claimed by M. Costantini in U.S. Pat. No. 5,003,109 or refluxing in toluene with SnCl2 as disclosed by J. A. Bellamy in J. Forensic Sci. 44, 603-608 (1999), and thermal decomposition as reported by J. C. Oxley et al in Propellants, Explosives, Pyrotechnics 27, 209-216 (2002). Although the methods degrade TATP to produce non-explosive byproducts, these methods are not in situ techniques and thus require disturbing the TATP contamination. MgPd has been investigated, in the present invention, as a reductive catalytic system that can cleave to the TATP ring and produce non-explosive byproducts.
A technology that can aid in the in situ treatment of TATP contaminated areas is disclosed that uses MgPd with emulsified zero valent metal (EZVM) technology. The outer oil membrane of the EZVM absorbs TATP crystals, which can be degraded by MgPd within the inner aqueous layer. This EZVM technology would permit the treatment of both wet and dry TATP contamination.
The following US Patents are related to degradation or removal of deleterious materials, including explosives.
U.S. Pat. No. 4,641,566 to Pomeroy teaches an in situ method for detecting buried land mines by non-destructive means involving the spraying of a suspected area with a leach of ionized metal and leaching the ionized metal into the soil to leave a metallic concentrate on an impervious object, such as a plastic mine; then, scanning the area with a metal detector.
U.S. Pat. No. 4,908,323 to Werner discloses a method for determining organic peroxides in aqueous and organic solutions using a peroxide detecting amount of a titanium (IV) compound.
U.S. Pat. No. 5,434,336 to Adams et al. describes an in situ process for the destruction of explosives by heating in the presence of elemental sulfur at temperatures below their spontaneous decomposition temperatures.
U.S. Pat. No. 6,664,298 to Reinhart et al. describes the in situ use of a zero-valent metal emulsion to dehalogenate solvents, such as, trichloroethylene (TCE) and other halogentated hydrocarbons that contaminate ground water and soil environments. The preferred zero-valent metal particles are nanoscale and microscale iron particles.
U.S. Pat. No. 6,767,717 to Itzhaky et al. describes a method of detecting a peroxide-based explosive in a sample suspected of having such an explosive; the method includes dissolving the sample in an organic solvent, then contacting the solution with an aqueous solution of a strong acid capable of decomposing the explosive to release hydrogen peroxide, and further contacting the mixture with a peroxidase enzyme to produce a pronounced change in the color of the substrate or its color intensity.
U.S. Pat. No. 6,773,674 to Bannister et al. describes methods and systems for detecting the presence of an energetic material, such as triacetone triperoxide (TATP), in a sample which is known to have the energetic material using thermal analysis for detecting and identifying explosives and other controlled substances. This method requires moving the explosive materials to a laboratory with appropriate analytical equipment.
U.S. Pat. No. 7,077,044 to Badger et al. discloses a method for bioremediating undetonated explosive devices by mixing an explosive mixture with microorganisms.
U.S. Pat. No. 7,159,463 to Dayagi et al. discloses a sensitive and selective method and device for the detection of trace amounts of a substance. A piezoelectric crystal element is used in a sensor device for identifying at least one foreign material from the environment.
WO1999/043846 to Keinan et al. discloses a method and kit for the detection of explosives. The method relies on the decomposition of TATP in the presence of concentrated aqueous sulfuric acid to produce hydrogen peroxide, which is detected by horseradish peroxidase and a color-change reagent.
J. A. Bellamy in J. Forensic Science 1999, 44(3), 603-608 reports that solutions of TATP in acetone and other organic solvents have been known to detonate, although solutions in toluene appear to be somewhat stable. It is therefore a risky proposition to dissolve the explosive in organic solvent in an attempt to remove it if no remediaton step is involved.
Irradiation with UV light has been used as a method of decomposing TATP in a detection scheme involving horseradish peroxidase/indicator combination as reported by R. Shulte-Ladbeck, et al. in “Trace Analysis of Peroxide-Based Explosives” Analytical Chemistry 2003, 75, 731-735.
The thermal decomposition of TATP has been found to have an activation energy which is within the reasonable expectation for a unimolecular decomposition initiated by a peroxide bond homolysis according to J. C. Oxley et al. in “Decomposition of a Multi-Peroxidic Compound Triacetone Triperoxide (TATP)” Propellants, Explosives, Pyrotechnics, 2002, 27, 209-216. Thermal decomposition of TATP in refluxing toluene has been found to be a slow process as reported by N. A. Milas et al. in “Studies in Organic Peroxides XXIV. Preparation, Separation and Identification of Peroxides Derived from Diethyl Ketone and Hydrogen Peroxide.”J. Am. Chem. Soc. 1959, 82, 3361-3364.
The complexation of TATP with ions was investigated by F. Dubnikova, et al. and many ions are calculated to form stable complexes with the explosive, as reported in “Novel Approach to the Detection of Triacetone Triperoxide (TATP): Its Structure and Its Complexes with Ions” J. Phys. Chem. A2002, 106, 4951-4956.
Further research is available on the use of nano-size elemental metal particles, such as, iron in emulsion systems capable of degrading chlorinated hydrocarbons in a controlled manner, the use of nanometal particles in emulsion systems where the reductive reactions take place within an emulsion droplet and where the hydrophilic and hydrophobic properties of the skin of the droplet can be controlled to a level so as to facilitate the entrance of the molecule of choice that is to be degraded. See C. L. Geiger, et al. “Nanoscale and Microscale Iron Emulsions for Treating DNAPL.” in: Innovative Strategies for the Remediation of Chlorinated Solvents and DNAPL in the Subsurface. Series 837, 2002, ACS Books, Washington D.C. Jacqueline Quinn, et al. “Evaluating The Distribution Of Emulsified Zero-Valent Iron For Four Different Injection Techniques,” Remediation of Chlorinated and Recalcitrant Compounds 2004, May 2004. Battelle Press, ISBN # 1-57477-132-9. Jacqueline Quinn, et al. “Field Demonstration of DNAPL Dehalogenation Using Emulsified Zero-Valent Iron,” 2005, Environ. Sci. Technol. 2005; 39(5); 1309-1318.
Kristen Milum, et al. in “In Situ Heavy Metal Contaminant Removal Using Emulsified Iron,” Remediation of Chlorinated and Recalcitrant Compounds 2004, May 2004. Battelle Press, ISBN # 1-57477-132-9 discuss various complexing agents that can be added along with nano-size metal particles into the emulsion system.
Collectively, the above references do not provide a composition of matter and in situ methodologies that safely degrade triacetone triperoxide (TATP), other organic peroxides that are “homemade” weapons of choice and nitro explosives that are becoming environmental pollutants in the soil, groundwater and other contaminated structures. There is a great need for a composition and method that provides safe and effective means for in situ degradation of explosive materials; the present state of the art does not meet this need.
Bimetals, FeNi, FePd, and MgPd, in combination with other technologies including bimetallic treatment systems (BTS) reported by K. B. Brooks et al. in Proceedings of the International Conference on Remediation of Chlorinated and Recalcitrant Compounds, 5th, Monterey, Calif. (May 22-25, 2006) and emulsified zero valent metal (EZVM) discussed by J. Quinn et al. in Environ. Sci. Technol. 39(5) (2005) supra provide a potential in situ method for remediating TNT and RDX contamination in groundwater, soil, and structures.